JP3882457B2 - Axial plunger pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an axial plunger pump having a mechanism for converting a rotary motion of a rotary shaft into a reciprocating motion of a plunger by swinging a swash plate, and more particularly to a pump having a slipper between a swash plate and a plunger.
[0002]
[Prior art]
In a conventional axial plunger pump, for example, as shown in Japanese Patent Laid-Open No. 5-113173, compressed oil pressure is supplied from a compression chamber of a cylinder to a contact portion between the slipper and the plunger through a through hole of the plunger. .
[0003]
Further, in the above pump, a through hole is also provided in the slipper, and the compressed oil is guided between the sliding contact surfaces of the slipper and the swash plate to ensure the oil film mainly by static pressure.
[0004]
Also, the lubrication between the contact surfaces of the slipper and the plunger is ensured by the squeeze effect that occurs when the plunger repeats the suction and compression processes and the suction effect of the lubricating oil that occurs when the spherical surface of the plunger tip swings. ing.
[0005]
[Problems to be solved by the invention]
In the above prior art, since high pressure oil is guided from the compression chamber to the sliding portion of the slipper, part of the working fluid is leaked, and the volumetric efficiency is deteriorated.
[0006]
Further, when it is desired to isolate the working fluid from the fluid for lubricating the slipper sliding portion, the two fluids are mixed and the structure is not established.
[0007]
Moreover, when the structure which has the return spring of a plunger is taken, the oil film formation effect by the side of a slipper spherical surface by the said squeeze effect reduces.
[0008]
Further, when the swash plate angle or the oblique axis angle is extremely small, the effect of drawing in the lubricating oil is reduced.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a pore that communicates the front and back of the slipper is provided at the center of the slipper, and the sliding pressure between the swash plate and the slipper causes the dynamic pressure of the lubricating oil generated on the sliding surface of the slipper to slip. The lubricating oil supplied to the swash plate surface is leaked from the sliding contact portion between the slipper and the plunger by using this dynamic pressure.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a structural diagram of a high-pressure gasoline pump for a gasoline direct injection engine having an embodiment of the present invention.
[0011]
When a rotational force from a camshaft of an engine (not shown) is transmitted to the shaft 2 via the coupling 1, the shaft 2 rotatably supported by the casing 3 via the radial bearing 4 and the thrust bearing 5 rotates. To do. The shaft 2 is integrally formed with a swash plate portion 2a having a plane 2aa inclined with respect to the axis of the shaft 2, and rotation and oscillation motion is generated in the plane 2aa when the shaft 2 rotates. . The slipper 6 having a flat surface portion 6a slidably contacting the flat surface 2aa and having a concave spherical surface portion 6b on the opposite side has a flat surface portion 6a and a concave spherical surface portion 6b communicating with each other through a pore 6c, and a plunger having a convex spherical surface portion 7a. 7 is moored so as to be rotatable and swingable. The plunger 7 is supported in a freely reciprocating manner in a bore hole 8a arranged circumferentially around the central axis of the cylinder 8. The cylinder 8 is sandwiched between the casing 3 and the rear body 13 and is fixed by the thrust of the tightening bolt 14. Low-pressure fuel sent by a feed pump (not shown) flows through a passage 13 a provided in the rear body 13 and flows into a low-pressure fuel chamber 8 d provided in the center of the cylinder 8.
[0012]
A suction valve 9 is provided inside the plunger 7, and the low-pressure fuel that has flowed into the low-pressure fuel chamber 8d passes through the communication hole 8e and is formed at a position where the suction passage 7b of the plunger 7 is opened. Flow into. Further, a return spring 10 is provided inside the plunger 7 to push the plunger 7 moved to the top dead center back toward the bottom dead center. When the plunger 7 reciprocates, the volume of the compression chamber 8c surrounded by the plunger 7 and the bore hole 8a contracts and expands repeatedly, thereby pressurizing the low-pressure fuel flowing in from the suction valve 9 to the bore hole 8a. High pressure gasoline is discharged from a discharge valve 11 provided at the bottom to a high pressure gasoline chamber 13b provided in the rear body 13.
[0013]
The oil chamber 3a, which is formed by being surrounded by the casing 3 and the cylinder 8 and contains the swash plate portion 2a, the slipper 6, and the convex spherical surface portion 7a of the plunger 7, stores oil for lubricating bearings and sliding portions. The low-pressure fuel chamber 8b and the oil chamber 3a are isolated by the shaft seal 12. The casing 3 is provided with an oil hole 3b for introducing oil supplied from the engine side (not shown) into the oil chamber 3a, and a part of the oil flowing in from the oil hole 3b is stored in the oil chamber 3a. And lubricate the sliding part. The surplus oil passes through the gap between the balls of the radial bearing 4 and returns to the cylinder head portion of the engine (not shown).
[0014]
FIG. 2 is an explanatory view of the sliding state of the slipper according to one embodiment of the present invention. In the oil chamber 3a in which oil is stored, the flat surface portion 6a of the slipper 6 moves on the flat surface 2aa of the swash plate portion 2a relative speed V. When sliding, the oil as the lubricant is interposed in the gap between the flat portion 6a and the flat surface 2aa, and dynamic pressure is generated. The load F obtained by integrating the pressure distribution p of the dynamic pressure over the area a where the dynamic pressure is generated is the force W that the plunger 7 presses the slipper 6, that is, the compression reaction force that the plunger 7 receives from the compression chamber 8b. It balances with the combined load due to the spring force of the spring 10. In addition, the pressure distribution p generated in the flat surface portion 6a of the slipper 6 during operation is assumed that there is no gap between the sliding contact portion of the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7, and no pressure leakage occurs. In the case, it tends to be highest in the central part. When it is assumed that there is no gap in the sliding contact portion between the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7 and no pressure leakage occurs, the pressure generated at the central portion of the flat surface portion 6a is defined as Pmax. When the pressure Pmax communicates with the concave spherical surface portion 6b by communicating with the pore 6c, the inner surface of the contact portion between the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7 (projected area A on the plane 2aa). ) Acts on the pressure Pmax. That is, the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7 are about to be separated with a load Fa = Pmax × A. When the area A is set so that the relationship F ≦ Fa is established between the loads F and Fa, the loads F and Fa must actually be balanced, and the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface of the plunger 7 A gap is generated at the contact portion of the portion 7a to cause an oil flow. Therefore, it is possible to secure an oil film on the spherical sliding portion. Furthermore, as shown in FIG. 3, by making the flat portion 6a of the slipper 6 convex, the pressure distribution p can be changed even if the load F does not change, and the pressure Pmax generated in the center portion can be increased. It becomes possible. However, in the actual pressure distribution, when an oil film (oil flow) exists between the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7, as shown in FIG. Needless to say, it has dropped to max. In addition, when the concave spherical surface portion 6b of the slipper 6 and the convex spherical surface portion 7a of the plunger 7 are in contact with each other with an annular contact width S as shown in FIG. 5, the pressure distribution generated on the concave spherical surface portion 6b side is trapezoidal. In such a case, if the pressure receiving area is set at least by the annular inner contact portion (area A ″), it can be handled in the same manner.
[0015]
In addition, when there is a restriction on the shape, lubrication environment, and surface roughness of the sliding portion and the area A cannot be sufficiently taken, a porous material having pores represented by a sintered material is used as the material of the slipper 6. It is also effective in terms of lubrication to supplement the supply of lubricating oil to the concave spherical surface portion 6b. Further, when the sliding portion of the slipper 6 slides under disadvantageous conditions for lubrication, a hard oxide film (Fe ₃ O ₄ ) is formed on the sintered material by steam treatment to prevent plastic flow on the surface. It is also possible to improve wear resistance and seizure resistance. It is also effective in improving seizure resistance to use martensitic stainless steel as the material of the slipper 6 and to form a nitride layer on the sliding surface of the slipper 6. As a matter of course, the wear resistance and seizure resistance of the slipper 6 are improved by making the mating material, that is, the material of the swash plate 2a and the plunger 7 excellent in slidability. As a material for the swash plate 2a, for example, it is also effective to use spheroidal graphite cast iron that exhibits the self-lubricating action of graphite existing on the surface of the flat surface 2aa. Further, as a material for the plunger 7, for example, an alloy tool steel is used, and a method of forming a nitride layer on the sliding surface is also effective.
[0016]
In this embodiment, when the fine hole is provided in the center of the slipper, the amount of wear at the sliding contact portion on the plunger side of the slipper is reduced to about 1/7.
[0017]
In addition, when the sliding contact surface side of the slipper with the swash plate was formed as a convex spherical surface of 2.5 microns, the wear amount of the sliding contact portion on the plunger side of the slipper was reduced to 1/90 to 1/160.
[0018]
According to this embodiment, it is possible to form an oil film on the slipper sliding portion without supplying high pressure to the slipper sliding portion from the compression chamber through the through hole of the plunger, thereby suppressing the leakage of the working fluid. And volumetric efficiency is improved.
[0019]
Furthermore, by providing a shaft seal between the plunger and the cylinder, it becomes possible to isolate the working fluid from the fluid for lubricating the sliding portion of the slipper.
[0020]
Even when the plunger is always pressed against the slipper by the return spring of the plunger, it is possible to form the oil film on the spherical surface of the slipper without expecting a squeeze effect.
[0021]
Even when the swash plate angle or the oblique axis angle is extremely small, it is possible to form an oil film on the slipper spherical surface side without expecting the effect of drawing the lubricating oil by the swinging motion of the spherical surface portion.
[0022]
【The invention's effect】
According to the present invention, the lubricating oil supplied between the swash plate and the slipper enables not only the lubrication between the swash plate and the slipper, but also the lubrication between the slipper and the plunger.
[0023]
In addition, since the dynamic pressure of the lubricating oil acts between the swash plate and the slipper and between the slipper and the plunger, the mutual metal contact is relaxed, and as a result, wear due to sliding between them is reduced. .
[Brief description of the drawings]
FIG. 1 is a structural diagram of a high-pressure gasoline pump for a gasoline direct injection engine having an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a sliding state of a slipper in one embodiment of the present invention.
FIG. 3 is an explanatory view of slipper plane side pressure distribution improving means in one embodiment of the present invention.
FIG. 4 is an explanatory diagram of slipper plane pressure distribution in one embodiment of the present invention.
FIG. 5 is an explanatory diagram of slipper spherical surface side pressure distribution in one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Coupling, 2 ... Shaft, 2a ... Swash plate part, 2aa ... Plane, 3 ... Casing, 3a ... Oil chamber, 3b ... Oil hole, 4 ... Radial bearing, 5 ... Thrust bearing, 6 ... Slipper, 6a ... Plane Part, 6b ... concave spherical part, 6c ... fine hole, 7 ... plunger, 7a ... convex spherical part, 7b ... suction passage, 8 ... cylinder, 8a ... bore hole, 8b ... low pressure fuel chamber, 8c ... compression chamber, 8d ... Low pressure fuel chamber, 8e ... communication hole, 9 ... suction valve, 10 ... return spring, 11 ... discharge valve, 12 ... shaft seal, 13 ... rear body, 13b ... high pressure gasoline chamber, 14 ... tightening bolt.

Claims (6)

A swash plate disposed between the reciprocating plunger, possess the swash plate in sliding contact slipper,
The plunger is formed in a convex spherical shape on the contact surface side with the slipper,
The contact surface side of the slipper with the plunger is formed as a concave spherical surface,
In a state where both are in contact, a minute space surrounded by the concave and convex spherical surfaces is formed,
In the slipper provided with pores connecting the space and the sliding contact surface of the slipper with the swash plate ,
Integral value F of dynamic pressure generated in the convex spherical surface portion of the slipper due to sliding of the flat surface of the swash plate and the convex spherical surface portion of the slipper (however, the sliding contact portion of the concave spherical surface portion of the slipper and the convex spherical surface portion of the plunger) Is a dynamic pressure P max generated at the center portion on the flat side of the slipper (however, the sliding contact between the concave spherical surface portion of the slipper and the convex spherical surface portion of the plunger). Of the slipper concave spherical surface portion and the sliding contact portion of the plunger convex spherical portion with the area A on the inner side (however, the projected area on the flat surface side of the slipper) of the slipper concave spherical surface portion The product is F ≦
P max × A The area A is defined so that
The dynamic pressure generated in the sliding contact surface portion with the swash plate of the slipper is guided to the minute space through the pores,
The concave spherical surface provided on the back surface of the slipper by the action of the dynamic pressure and the sliding contact surface portion of the convex spherical surface of the tip of the plunger are separated so that a minute gap is generated,
Therefore, the lubricating oil flowing through the pores and through the minute spaces and minute gaps
An axial plunger pump configured to create a flow . A key Shall plunger pump according to claim 1 formed with the sliding surface side of the slipper of the swash plate in a convex shape. The axial plunger pump according to claim 1, wherein the slipper is made of a sintered material having pores, or a material in which a hard oxide film (Fe ₃ O ₄ ) is formed on the sintered material by steam treatment. The axial plunger pump according to claim 1 , wherein martensitic stainless steel is used as a material of the slipper, and a nitride layer is further formed on the sliding surface of the slipper. The axial plunger pump according to claim 1 , wherein spheroidal graphite cast iron is used as a material of the swash plate. The axial plunger pump according to claim 1 , wherein alloy material is used for the plunger material and a nitride layer is formed on the sliding surface of the plunger.

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